Earlier this month, officials in the South Pacific island nation of Tuvalu had to confront a pretty dire problem: they were running out of water. Due to a severe and lasting drought, water reserves in this country of 11,000 people had dwindled to just a few days' worth. Climate change plays a role here: as sea levels rose, Tuvalu's groundwater became increasingly saline and undrinkable, leaving the island dependent on rainwater. But now a La Niña–influenced drought has severely curtailed rainfall, leaving Tuvalu dry as a bone. "This situation is bad," Pusinelli Laafai, Tuvalu's permanent secretary of home affairs, told the Associated Press earlier this month. "It's really bad."

So far Tuvalu has been bailed out by its neighbors Australia and New Zealand, which have donated rehydration packets and desalination equipment. But the archipelago's water woes are just beginning — and it's far from th…